1. Actually what happening is particle's scale decrease during its lifetime. But usually particles moves away from skeleton, so particle size correlate with distance to skeleton. Feed Particle SOP into two different SOPto CHOPs:sopto1: scope "life" attribute rename it to "l1 l2" (or smth else) and use Math CHOP to subctract one from anothersopto2: scope "P" and rename to "tx ty tz"merge these CHOPs and use for GEO instancing

2. Noise SOP with attribute "Point normals"

One more tip: use Kinect CHOP and combination of Select CHOPs and CHOPto SOPs to make SOP skeleton (you can use points or lines).